1. Field of the Invention
This invention relates to apparatus used to screw together (or “make up”) and unscrew (or “break out”) threaded tubular connections joining sections (frequently called “joints”) of tubulars. Such tubulars are frequently used in the drilling, servicing and completion of oil and gas wells, in the form of drill pipe, tubing, and other similar tubular goods. Such apparatus are commonly referred to as “tong units” or “power tongs,” which use toothed dies carried by tong jaws, to transmit torque to the tubular connection. It is to be understood that the term tong unit, for purposes of this application, encompasses both the power tong portion of the tong unit (that is, the part that turns one side of the tubular connection) and the backup portion of the tong unit (that is, the part which holds the other side of the tubular connection).
In more detail, this invention relates to a tong unit which comprises dumbell rollers and a ring gear having mating, circumferential load support surfaces, both vertical (i.e. substantially parallel to the rotational axis of the ring gear of the tong), and angled or inclined to the ring gear rotational axis; and a dumbell roller shaft mounting system, as more particularly described herein.
2. Related Art
By way of background, a typical tong unit will be described in sufficient detail to enable those having ordinary skill in the relevant art field to understand how the present invention is incorporated therein.
Tong Units Generally
With reference to FIG. 1, a tong body 10 carries a gear system, generally referred to as 20, which is driven by a motive source, typically a hydraulic motor 30. As is well known in the art, rotation of the motor turns the gears, which turn ring gear 40; as can be readily appreciated, ring gear 40 thereby has a rotational axis (for clarity, denoted as RA in FIG. 2), about which ring gear 40 rotates. The rotary movement of ring gear 40, and thereby torque, is transmitted from ring gear 40 to a jaw assembly referred to in globo as 50, thence to dies 60 carried in the jaw assembly, and ultimately to a tubular connection 70 (shown in cross section), by the dies pressing against and/or biting into the metal of the connection. As is known in the art, the jaws are held within the ring gear by cage plates both above and below the ring gear, not shown in FIG. 1 for clarity.
Although the present invention has applicability to both closed- and open-throat tongs, by way of illustration an open throat tong will be used in the description of the invention. The ring gear in an open throat tong has a cut-out, as can be seen in the drawing, to permit the tubular to be moved into and out of the gripping region of the tong. Said another way, the ring gear in an open throat tong does not form a complete circle, but has a section cut out of the circle.
Prior Art Ring Gear Support
The ring gear in a power tong must be supported both vertically and horizontally by the tong body, transferred through intervening structural elements, including the dumbell rollers described herein. The primary vertical load generated by the ring gear is its weight. The primary horizontal load generated by the ring gear arises out of “spreading” (that is, the tendency of the open throat of the ring gear to open further) of the ring gear as it comes under load. Both the vertical load and the horizontal load must ultimately be transferred to the tong body.
Both the vertical and horizontal loads are primarily transferred from the ring gear to a plurality of so-called “dumbell rollers,” named for their shape, as can be readily seen in FIGS. 2 and 3 (element 100; see also FIG. 4 for the general shape of a dumbell roller). Prior art dumbell rollers and ring gears both had square (or nearly square) shoulders forming the vertical support for the ring gear (namely, forming a horizontal support surface, to take vertical loads); the bottom horizontal surface of the ring gear teeth (i.e. the “sides” of the teeth) contacted the horizontal surface of the dumbell roller, providing the required vertical force. As can be readily understood, that arrangement tended to wear the ring gear teeth and dumbell rollers.
In addition, prior art dumbell roller arrangements comprised a dumbell roller retainer arrangement which could result in binding of the roller, under one set of conditions; or excessive wear between various parts, under other conditions.